Enzymes capable of hydrolyzing granular starch at temperatures below the starch gelatinization temperature are known in the art. For instance, it has long been known that alpha-amylases can hydrolyze granular starch, as disclosed in, for instance, Richert et al., Publication of the Carnegie Institution at Washington, No. 173, Part 1 (1913). More recently, other enzymes, such as glucoamylase enzymes, have also been found to hydrolyze granular starch below the starch gelatization temperature. It is believed that the presence of a starch-binding domain is essential for an enzyme to hydrolyze granular starch; numerous enzymes having such domains are known, as disclosed, for instance, in Walker, G. J. et al. Biochemical Journal, 86:452 (1963); Belshaw, N.J. et al., Biochim. Biophys. Acta, 1078:1117-20 (1991), and Svensson, B. et al., Eur. J. Biochem., 154:497-502 (1986). As is well known in the art, the term “enzyme hydrolysis” refers to enzyme-catalyzed hydrolysis, and thus enzymes such as alpha-amylase can be regarded as “hydrolyzing” starch via a catalytic hydrolytic action.
As is also known in the art, when a granular starch is treated with an alpha amylase or a glucoamylase, the granular structure of the starch degrades, leaving behind a porous starch granule upon partial hydrolysis of the starch, or, if the enzymatic hydrolysis is allowed to continue, yielding a starch hydrolyzate or ultimately glucose or another lower order sugar. It is also recognized that the enzymatic attack on starch granules takes place by exo-corrosion in which the enzyme either erodes the entire surface of the granule or digests a channel from points on the surface towards the center of the granule. In the latter mode of attack, once the center is reached, the enzymatic attack proceeds outwardly from the center over a broader front. The internal structure of a porous starch granule that has been so modified is open and cavernous and can exhibit either a terraced or a step-shaped appearance.
When a glucoamylase enzyme is allowed to completely hydrolyze a starch granule, the resulting product typically is glucose. U.S. Pat. Nos. 2,583,451; 3,922,198; 3,922,199; 4,612,284; and 4;618,579 disclose processes for converting granular starch to glucose by treating of the starch with glucoamylase or a mixture of glucoamylase with alpha-amylase. Other reaction products are possible; for instance, U.S. Pat. No. 3,922,201 discloses a process for the preparation of levulose-containing compositions from granular starch by treating the starch with alpha-amylase, glucoamylase, and glucose isomerase.
The prior art also has described the enzymatic hydrolysis of starch below the gelatinization temperature to produce starch hydrolyzes other than glucose. For instance, U.S. Pat. No. 3,922,196 discloses a process for converting granular starch to a starch hydrolyzate having a DE (dextrose equivalent) between 40 and 55 and including a high percentage of disaccharides and trisaccharides. The process disclosed in this patent employs alpha-amylase, glucoamylase, beta-amylase and isoamylase. Another document, U.S. Pat. No. 4,113,509, discloses an enzymatically produced high maltose-maltotriose starch hydrolyzate having a DE of 40 to 55. This patent discloses a process in which alpha-amylase, alone or with a saccharifying enzyme such as glucoamylase or beta-amylase, is used to hydrolyze the starch. Methods for the production of other malto-oligosaccharides such as maltose and maltotetraose by treatment of starch with specific alpha-amylases have also been employed on an industrial scale.
The prior art also has provided applications for porous starches that are obtained by partial enzymatic digestion of the granular starch. For instance, U.S. Pat. No. 4,985,082 discloses a starch matrix material comprising granular starch that is partially hydrolyzed with an alpha-amylase and/or a glucoamylase and treated chemically to modify the structural integrity and surface characteristics of the starch. The disclosed starches are said to be useful as adjuvants for antiperspirants and as bulking agents for foods and drinks. U.S. Pat. No. 4,551,177 discloses a compressible starch said to be useful as a binder for a tablet or capsule and which is said to be prepared by treating granular starch with an acid and/or with an alpha-amylase enzyme at a temperature below the gelatinization temperature of the starch. Yet another document, U.S. Pat. No. 5,445,950, discloses a method of using alpha amylase to prepare slightly decomposed starch granules having low viscosity. The starch granules are said to be useful as a raw material in the starch and sugar industry. U.S. Pat. No. 5,904,941 discloses a viscosifier that comprises an enzymatically hydrolyzed, ungelatinized granular starch with a dextrose equivalent of from about 5 to 60. Still another document, U.S. Pat. No. 5,935,826, discloses a modified starch prepared by the glucoamylase hydrolysis of a starch derivative that contains a hydrophobic group or both a hydrophobic and a hydrophilic group. The starches are said to be characterized by having a DE from 20 to 80, and are said to be useful as emulsifiers or an encapsulating agents. International Patent Publication WO 96/10586 discloses a method for preparing a fat substitute based on hydrolyzed granular starch. U.S. Pat. No. 5,919,486 discloses a powder preparation that comprises a porous starch grain carrier and a material carried within the pores of the carrier, the porous starch grain carrier having been prepared by partially hydrolyzing starch with raw starch digestive enzyme.
Other starches also have been used in dusting powder applications for many years, primarily to absorb more fluids from the skin. For example, U.S. Pat. No. 4,568,539 discloses compositions said to exhibit excellent moisture absorbency and comprising starch and a specific pregelatinized starch. Another document, EP 182,296, discloses a body dusting powder that comprises a porous starch granule which consists essentially of the residue remaining after about from 45% to 95% by weight of the granular starch has been solublized with an enzyme.
Skin fluids found on the skin surface typically comprise a complex mixture of sebum, lipids, sweat, and environmental or applied material. Because such fluids can provide nutrients and a moisture-rich environment for microorganism to proliferate, such fluids can cause body odors and even in some cases bacterial and fungal infections. These effects can be mitigated by applying a fluid-absorbing effective amount of a powdered starch composition as described in the prior art, or other known absorbents such as talc, cellulose derivatives, and so forth. The aforementioned starch-based compositions are said to control excess moisture, (i.e. the aqueous component of skin fluid), but are not said to control the oily secretions produced by sebaceous glands.
It is a general object of the invention to provide a method for preparing a fluid absorber that is effective in absorbing oil from the skin, and, more generally, that is effective in absorbing fluid from the skin. In other embodiments it is a general object to provide a fluid absorber.